Saturday, November 12, 2016

Carbon Upcycling

From a team of researchers at the University of Illinois-Chicago comes news of a technology with the potential to slow the rate of increase of carbon dioxide levels in the atmosphere. The research was recently published in Science and reported on the TakePart blog. The prototype shown above might resemble any number of electronics projects I put together as a kid, but it is more like a leaf than anything else.

The researchers have found a way to capture carbon dioxide from the atmosphere in a way that allows them to produce usable fuel, using techniques and materials that make the process more efficient than heretofore possible.

When the fuel is burned, it returns carbon dioxide to the atmosphere, so this is not a technique for long-term carbon sequestration. It is, rather, a carbon-neutral way to replace fossil fuels; the timing of the extraction of carbon dioxide from the atmosphere makes all the difference. It is analogous to using firewood (as I am doing right now) instead of coal to heat one's home.

Firewood cut by a local tree service; stacked in my garage this morning.

The firewood example is instructive; as I write this, a fire in my fireplace is returning carbon dioxide to the atmosphere. It was removed from the atmosphere by the process of photosynthesis within recent decades, is being returned to the atmosphere as I write this, and will again be taken out of the atmosphere by new trees growing where these were removed. The entire cycle might last 50 to 100 years or so, and the effect on the climate is nil.

Global levels of carbon dioxide since the onset of industrial uses of fossil fuels. The concentration has grown from 280 ppm to over 400 pmm, with 350 ppm a goal of many experts interested in finding a level that would facilitate adaptation measures.

This graph is known as the Keeling Curve, which shows the levels of carbon dioxide in the atmosphere. It is a trace gas -- still less than 1/20th of one percent of the atmosphere -- but a very important one because of its ability to trap outgoing energy in the infrared portion of the spectrum. Gases of this kind are called greenhouse gases, and without them Earth would be no more livable than the moon. My Frosty Denial post explains the basic physics of the relationship between increased concentrations of these gases and increased temperatures.

Prior to the Industrial Revolution in Europe and North America, carbon dioxide accounted for 280 parts per million (ppm) of the atmosphere -- 0.028 percent. As measured in the tiny bubbles of air recovered from ice cores, the quantity barely changed as fossil-fuel use increased in just one small part of the world. But as industrial uses of oil, coal, and natural gas increased and broadened geographically, the concentration steadily increased as well.

That dinosaur in the gas tank was not real, for two reasons. The organic material in fuel is plant, not animal biomass. And the dinosaurs are far too young.

The key to understanding the increase is understanding the role of time. All of the carbon dioxide released into the atmosphere by the burning of fossil fuels originated in that very same atmosphere. It was removed by the process of photosynthesis, building plant biomass that would eventually be compressed and transformed into coal, mainly during the Carboniferous period. Most of the world's coal was formed from plant materials over a 60,000,000 period that ended 299,000,000 years ago.

It is difficult to imagine just how long ago this was; for comparison, keep in mind that dinosaurs did not start to appear until the Mesozoic Period, more than 50,000,000 years after most of the coal had been deposited, The story is similar for oil and natural gas -- most of it was formed over a very long time period, very long ago. Within the first 200 years of industrialization, humans have burned something close to half of the fossil fuels, releasing the carbon back to the atmosphere thousands of times more rapidly than it was withdrawn.

In retrospect, it is no surprise that this increased the concentration of carbon dioxide from 280 ppm to 350 ppm by the time I entered college in the 1980s, and to 400 ppm and beyond during my adult life (so far). The perils caused by this increase include rising seas, shifting crop seasons, and the steady creep of tropical blights and diseases into formerly temperate regions. No longer a future worry, the changes are widely apparent and developing so rapidly that no single remedy can be considered sufficient. Improvements in technology need to be coupled with changes in the uses of energy, as well as measures to protect the most vulnerable people.

At this point, the key question about the carbon-capturing technology described above is whether it can be deployed at a sufficient scale and efficiency to be economically viable. If it is successful, it could help to slow the rate at which carbon dioxide continues to increase in the atmosphere. For the reasons described above, it cannot actually bring those levels DOWN -- only slow their increase. Even if this becomes a "silver bullet" technology, we will have to do much more to protect Earth's climates.

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